mytime{ int a; /* 4 byte */ time_t t; /* 4-8 byte */ int b; /* 4 byte */ }; int main(int argc, char *argv[]){ printf("sizeof(int) = %lu\n", sizeof(int)); printf("sizeof(long) = %lu\n", sizeof(long)); printf("sizeof(time_t) = %lu\n", sizeof(time_t)); printf("sizeof(struct mytime) = %lu\n", sizeof(struct mytime)); return 0; } $ make gcc -Wall -g -c src/time64.c -o src/time64.o gcc -Wall -g -o a.out src/time64.o